Astronomical instrument.



No. 728,916. PATENTED MAY 26, 1903.

E. G. HEWITT.

ASTRONOMIGAL INSTRUMENT.

APPLICATION FILED JULY 11, 1902.

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No. 728,916. PATENTED MAY 26, 1903.

' E. G. HEWITT.

ASTRONOMIGAL INSTRUMENT.

APPLICATION FILED JULY 11, 1902. N0 MODEL. 2 SHEETS-SHEBT 2.

Th2 Noam wurrw's co, Puovuurm), wAsnmgTum n c EDIVARD G. HEWITT,

Patented May 26, 1903.

PATENT OFFICE.

OF NEW YORK, N. Y.

ASTRONOMICAL INSTRUMENT.

SEECIFEGATION forming part of Letters Patent N 0. 728,916, dated May 26, 1903.

Application filed July 11,1902- Serial No. 116,282. (No model.)

To all whom it may concern:

Be it known that I, EDWARD G. HEWITT, a citizen of the United States, residing at New York, in the county of Kings, State of New York, have invented certain new and useful Improvements in Astronomical Instruments, of which the following is a specification, reference being had to the drawings accompanying and forming part of the same.

The invention forming the subject of my present application is an apparatus useful as an educational appliance for teaching astronomy, for determining the position of the heavenly bodies, or finding any of such bodies from known astronomical data. It may also be used as a snn dial by removing certain of its parts and substituting a pin forv casting the shadow on the graduated dial.

The apparatus is illustrated in the accompanying drawings, in which-- Figure 1 is a side view, partly in section, of my device. Fig. 2 is a perspective view of the triangular sighting device. Fig. 3 is a section on line I I of Fig. 1 of the base of my apparatus. Fig. 4 is a plan view of the right-ascension circle, showing the pointer which is attached to the sighting device and the auxiliary sighting device. Fig. 5 is a front view of the dial. Figs. 6 and 7 are details showing a convenient method of securing the shadow-pin in position for using the apparatus as a sun-dial. 8 is a detail View showing the base by which the apparatus is secured upon its support.

The device is designed to be set on and secured to a support, as a post 1, Fig. 1, by

means of a screw 2, passing through the base 3. Since a screw does not afford a sufiiciently firm and lasting engagement with the vertical grain of a post, I find it desirable to adopt the means shown most clearly in Fig. 3, in which 1 is a plug or bar set crosswise of the grain near the top of the post, into which the screw 2 penetrates, thus forming a very satisfactory and durable means of attachment.

To an angular extension 4. of the base is bolted a dial or plate 5. Since it is necessary that the dial be parallel to the plane of the equator, the angle which the extension 4. makes with the horizontal is determined by the latitude in which the instrument is used. I therefore make the angle of the extension with the base approximately that of the particular latitude; but in order that its use may not be confined strictly to one locality and to enable accurate adjustment to be made I provide the base with a curved bearing-surface 6 for the head of the attaching screw or bolt and make the bolt-hole large enough to give the base some play. This feature is shown more clearly in the perspective view, Fig. 8. Thus by driving a wedge under the base the instrument may be tilted forward or backward, the curved rib 6 always affording the same uniform bearing-surface, to adjust the dial to the proper angle with the horizon. To adapt the dial 5 to accurate adjustment in its own plane with respect to the vertical north-and-south plane, more particularly for a purpose to be described hereinafter, I employ a washer 7 of yielding material, having some resiliency, such as leather, in connection with the bolt 8. hen the dial is set in approximately the correct position, the nut 9 is tightened. Then the washer 7 will yield sufficiently to permit the dial to be shifted by striking it a smart blow oneither side.

Through a hole 10, Fig. 5, at the center of the dial is thrust the end of a standard 11, threaded to receive athumb-nut 12, which is tightened to secure the standard firmly in place perpendicular to the dial, as shown. On the standard, fitting snugly thereto but capable of rotation thereon, is a disk 13, Figs. 1 and 4, bearing the graduations shown from 0 to 23, thus being divided into twenty-four equal divisions and constituting a right-ascension circle. On its other end is supported the sighting device, Figs. 1 and 2. This latter consists of a triangular frame formed by a bar or base 16 at right angles to the tube 1 1 and the sides 17 18. The bar 18 has slidably mounted thereon a sight 19, which has a sight-aperture 20 and a setscrew 21. Near the opposite end of the bar 16 is another sight 22, fastened to the triangular frame.

Since the bar 18 is a chord or part of a chord of a circle whose center is at the sight 22, the radius 16 of the circle being parallel to the equator, graduations, as 23, maybe marked on the chord 18, corresponding to declination or distance from the celestial equator. Thus by sighting through the apertures 20 and 24 the declination of any star may be read off on the scale 18, or by setting the sight 19 for a given declination and arranging the device for the proper right ascension the star may be readily found. As arranged in Fig. 1, the eye of the observer being placed at the aperture 24 the instrument will show north declination; but if it is desired to read south declination with the same right ascension it is only necessary to rotate the triangular frame through one hundred and eighty degrees of arc and apply the eye then to the movable sight 19, as will be readily under- [5 stood. V

The triangular sighting device is a suitable form for declinations of about sixty degrees and under; but for declinations above that the altitude of the triangle increases so rapidly as the legs 17 18 become more nearly perpendicular to the base that the device becomes inconveniently large, and I therefore provide an auxiliary instrument 30 for the higherdeclinations. This consists, preferably, of a tube 31, Figs. 1 and 4, pivotally mount.- ed to swing in a plane perpendicular to the right-ascension circle on a rotatable arm 32 on the standard 11. A scale may be provided by which the positions of the tube may be determined in the usual manner; but in the device illustrated there are two stops 33 34, which limit the swing of the tube in lieu of a scale. The stops are so arranged that'in its extreme positions the tube Will point to two prominent stars of known declination, thereby enabling the observer to readily arrange the instrument for use. suppose in the position shown by the dotted lines the angle of the tube and plate 13 is the declination of one of the pointers. Then by sighting through the tube and rotating the arm 32 this star may be quickly located, and since its right ascension is known the plate 13 may be turned to bring the correct graduation under the index 35 of the arm 32, in which relation they are clamped by means of a set-screw 36. The device is now ready for use, and the right ascension of other stars may be read off by means of the pointer 15 of the triangular sighting device.

In order to use the instrument as a sun-dial during the day, the standard 11 is removed and a pin 25 fixed in the hole 26, the shadow of the pin on the divisions of the dial indicating the time. A convenient means for fastening the pin in place is shown in Figs. 6 and 7, in which 27 is a lock-screw set up firmly against the pin, as shown. A lock-pin 28, fitting in a groove 29 in the lock-screw, prevents the latter from being removed from the dial and carelessly lost. The two-part construction of dial and base, permitting lateral adjustment of the former, is of special value when the instrument is used as ,a sundial, since by this adjustment correction for For example,

equation of time may easily be made. Since apparent solar time and mean solar time are at certain periods of the year as much as a quarter of an hour apart, it is desirable that the error should be corrected. This adjustment is made by turning the dial on the pivot 8, thus, as will be readily understood, throwing the shadow of the pin backward or forward, as may be necessary for the correction. By reason of the yielding Washer, as before explained, the adjustment may be made accurately and without difficulty.

The apparatus described is a convenient and cheap form of my invention; but inasmuch as it is capable of many embodiments I do not consider myself limited to the precise form shown.

What I claim is- 1. In adevice of the kind described, a substantially plane base having an opening to receive a fastening-screw, and a curved bearing-s11 rface about said opening, curved in one direction only, and projecting above the base, as and for the purposes set forth.

2. In a device of the kind described, in combination, a base, and a sun-dial pivotally mounted on said base to swingin an east-andwest plane so as to be adjusted in the eastand-west plane of said dial, whereby a correction for equation of time may be readily made, as set forth.

3. In a device of the kind described, in combination, a plate, a graduated disk supported on said plate, and a sighting device rotatably mounted above said disk, provided with a declination-scale, and a pointer above said disk, movable in unison with saidsighting apparatus, as and for the purposes set forth.

4:. In a device of the kind described, in combination, a plate; a standard removably mounted thereon; a graduated disk on the standard; a sighting apparatus rotatably mounted on the standard, comprising a triangular frame having its base at right angles to the standard, a sight at one end of the base, and a slidable sight on the side of the frame opposite the first-mentioned sight, said side having a declination-scale; and a pointer over the disk, movable in unison with the sighting apparatus, as and for the purposesset forth.

5. In a device of the kind described, in combination, a plate, a standard thereon, a graduated disk on the standard, a sighting apparatus, and an auxiliary sighting apparatus rotatably mounted on said standard and movableindependently of the first-mentioned sighting apparatus, as and for the purposes set forth.

EDWARD Gr. HEWITT. 

